1. Field of the Invention
The present invention relates to inkjet printer heads and methods of fabricating the same. More particularly, the present invention relates to an inkjet printer head using a semiconductor wafer as a nozzle and to a method of fabricating the same.
2. Background of the Invention
Printers output information processed by a computer and may be classified into three types: dot matrix, inkjet and laser printers.
The dot matrix printer is an impact type of printer that uses carbon paper and is fading in popularity due to its low resolution and loud operation. The laser printer has advantageous operating characteristics of low noise, high speed and high resolution. However, the laser printer also has disadvantageous characteristics of high price and difficulty in printing with color.
On the other hand, the inkjet printer is widely used because of its low noise and facility in printing with color. Inkjet printers may be classified, according to the method in which they eject ink, as piezoelectric, bubble-jet and thermal inkjet printers. However, the bubble-jet printers are similar to the thermal printers in that each use heat for ejecting ink. Thus, inkjet printers may be generally divided into piezoelectric and thermal types of printers.
FIGS. 1 and 2 are a plan view and a cross-sectional view of a conventional inkjet printer head, respectively.
Referring to FIGS. 1 and 2, an opening 15 extends through a semiconductor wafer 10, i.e., between upper and lower surfaces thereof. An ink cartridge is attached to one side of the semiconductor wafer 10. Structures for ejecting ink are disposed on the other side of the semiconductor wafer 10.
The structures for ejecting ink comprise an orifice layer 75, an adhesive layer 70, and a resistor pattern 40. The orifice layer 75 and sidewalls of the adhesive layer 70 constitute an ink chamber 73 for accommodating ink supplied from the ink cartridge. The orifice layer 75 has a cylindrical opening that forms a nozzle portion 77 for focusing ink to one point. The adhesive layer 70 sticks the orifice layer 75 to the semiconductor wafer 10 and forms the sidewalls of the ink chamber 73. Preferably, a support layer 20, formed of an insulating material, is interposed between the resistor pattern 40 and the semiconductor wafer 10.
Heat generated in the resistor pattern 40 by electrical resistance increases the temperature of ink in the ink chamber 73. When the temperature of the ink exceeds the point at which the ink will evaporate, the pressure within the ink chamber 73 becomes high enough to eject ink from the nozzle portion 77 toward the paper.
Meanwhile, the piezoelectric printers differ from the thermal printers in that the piezoelectric printers use a mechanical contraction and expansion of piezoelectric materials for changing the pressure within the ink chamber 73.
According to the conventional printer, ink is supplied to the ink chamber 73 through the opening 15, and is then ejected outwardly from the nozzle portion 77 of the orifice layer 75. Moreover, the adhesive layer 70 and the orifice layer 75 are not formed during the forming of the opening 15 and the resistor pattern 40, but are attached to the semiconductor wafer 10 after being produced separately.
The nozzle portion 77 of the orifice layer 75 should be aligned with the center of the resistor pattern 40 for the ink to be ejected with a high degree of precision. However, the nozzle portion 77 and the resistor pattern 40 are fine structures having widths of several tens to several hundreds of micrometers. Thus, the nozzle portion 77 and the resistor pattern 40 may be misaligned when the orifice layer 75 is attached to the semiconductor wafer 10.
In addition, the ink chamber 73 delimited by the adhesive layer 70 and the orifice layer 75 should be connected with the opening 15 of the semiconductor wafer 10. Thus, the inner sidewalls of the adhesive layer 70 must have a somewhat complicated shape.
Furthermore, according to the conventional printer, the resistor pattern 40 is disposed on one side of the semiconductor wafer 10 as separated from the ink cartridge. This separation gives rise to a residual heat phenomenon, which prevents effective cooling of the resistor pattern 40. Accordingly, the resistor pattern 40 can become overheated and damaged.